noun (n)

• an urge to do or say something that might be better left undone or unsaid(noun.motive)

  Example:
  He felt a compulsion to babble on about the accident.
  

  Synonym:
  irresistible impulse
  

  source: wordnet30
• an irrational motive for performing trivial or repetitive actions, even against your will(noun.motive)

  Example:
  Her compulsion to wash her hands repeatedly.
  

  Synonym:
  obsession
  

  source: wordnet30
• using force to cause something to occur(noun.act)

  Example:
  Though pressed into rugby under compulsion I began to enjoy the game.
  

  Synonym:
  coercion
  

  source: wordnet30
• The act of compelling, or the state of being compelled; the act of driving or urging by force or by physical or moral constraint; subjection to force.(noun)

  source: webster1913